Universal joint yoke and method of making same

ABSTRACT

A metal sheet is cut to provide an elongated blank having five regions defined along the length of the elongated blank, the defined regions being a central region, two end regions, and an intermediate region between the central region and each of the two end regions. The elongated blank is bent such that the two end regions overlap and provide a mounting for a shaft and such that a pivot member to be mounted on the central region of the elongated blank will be in alignment, axially, with respect to the shaft. Bores may be formed in the intermediate regions for mounting of a cross-piece to pivotably connect the yoke to a coupling member.

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to universal joints and, moreparticularly, to yoke configurations for use with universal joints ofthe double Cardan type.

[0002] Intermediate shafts used in automobile steering columns requireone or more universal joints to maneuver the column around variousmechanical components. Operating angles of such universal joints haveincreased as vehicle engine compartments have become smaller and as rackand pinion steering systems have replaced recirculating ball steeringsystems. To accommodate the increased operating angles, simple universaljoints with a single pivotable cross-pieces joining two shafts have beenreplaced by double Cardan universal joints that have two pivotablecross-pieces and a mechanism to ensure that the operating angle isdistributed equally between the two pivotable cross-pieces.

[0003] Such double Cardan universal joints have two opposite end yokes,with a hub for joining each yoke to a shaft and branched arms defining afork opposite the hub. Two pivotable cross-pieces are mounted in thebranched arms of the yokes and link the yokes to a coupling yoke thattransmits torque between the two shafts. A central ball joint,comprising a spherical ball fixed on one yoke and a sleeve for receivingthe spherical ball fixed to the other yoke, controls the angle of theconnecting yoke with respect to each shaft. Such universal joints arewell known in the art. An example of a double Cardan universal joint ofthis type is illustrated in U.S. Pat. No. 5,820,467.

[0004] Although such designs have been effective, the high cost offorming the yokes and other components of such double Cardan universaljoints has limited their use. Typically, such yokes require a casting,forging or assembly of a multipiece blank, along with machining andother manufacturing processes that add significantly to the cost of theuniversal joint. Accordingly, there is a need for an improved designthat is suitable for manufacturing yokes for such double Cardanuniversal joints more simply, but without comprising the quality of theresulting universal joint.

[0005] The foregoing illustrates limitations known to exist in presentdevices and methods. Thus, it is apparent that it would be advantageousto provide an alternative directed to overcoming one or more of thelimitations set forth above. Accordingly, a suitable alternative isprovided including features more fully disclosed hereinafter.

SUMMARY OF THE INVENTION

[0006] In one aspect of the invention, this is accomplished by providinga method of making a yoke for a double Cardan universal joint. Themethod comprises cutting a metal sheet to provide an elongated blankhaving five regions defined along the length of the elongated blank, thedefined regions being a central region, two end regions, and anintermediate region between the central region and each of the two endregions. The elongated blank is bent such that the two end regionsoverlap and provide a mounting for a shaft and such that a pivot memberto be mounted on the central region of the elongated blank will be inalignment, axially, with respect to the shaft.

[0007] In another aspect of the invention, this is accomplished byproviding yoke for a double Cardan universal joint, the yoke being madeaccording to a particular method.

[0008] The foregoing and other aspects will become apparent from thefollowing detailed description of the invention when considered inconjunction with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0009]FIG. 1 is a plan view of an elongated blank comprising anintermediate product during the making of a yoke for a double Cardanuniversal joint according to an embodiment of the present invention;

[0010]FIG. 2 is a lateral view of a yoke for a double Cardan universaljoint made by applying additional manufacturing steps to the elongatedblank of FIG. 1;

[0011]FIG. 3 is a cross sectional view of a variation of the yoke for adouble Cardan universal joint illustrated in FIG. 2, corresponding tothe line 3-3 of FIG. 2; and

[0012]FIG. 4 is a plan view of an elongated blank comprising anintermediate product during the making of a yoke for a double Cardanuniversal joint according to another embodiment of the presentinvention.

DETAILED DESCRIPTION

[0013] Referring now to FIG. 1, an elongated blank 10, illustrating thepresent invention, comprises five regions defined along the length ofthe elongated blank 10, the defined regions being a central region 12,two end regions 14 and 16, and two intermediate regions 18 and 20, eachintermediate region 18 or 20 being between the central region 12 and oneof the two end regions 14 and 16, respectively. For convenience, theelongated blank 10 can be cut from a metal sheet of uniform thickness.The material may be mild steel, for example, or other suitable material.

[0014] The elongated blank 10 is bent such that the two end regions 14and 16 overlap and provide a mounting for a shaft, not shown. Theresulting shape facilitates the mounting of a pivot member, not shown,such that the pivot member is in alignment with an axis corresponding tothe shaft. One possible bent form 22 for the elongated blank 10 isillustrated in FIG. 2. To form bent form 22, the elongated blank 10 hasbeen bent, predominately, at predetermined locations, approximately atthe junctures between the five regions, such that the bent form has asubstantially rectangular longitudinal section, with central region 12being parallel to and opposite the two overlapping end regions 14 and16, and with the two intermediate regions being parallel and oppositeeach other.

[0015] To facilitate mounting of the shaft on the overlapping endregions 14 and 16, the end regions 14 and 16 may have non-circular bores24 and 26, formed before, during or after the elongated blank 10 is cutfrom metal sheet, thereby providing a keyed mounting for the shaft. Inthe embodiment of FIGS. 1-3, the non-circular bores 24 and 26 arehexagonal, however other shapes, for example internal splines, may beused. The shaft may be solid or hollow, may have a circular ornon-circular cross section, and may be fixed by interference fit,welding, staking, orbital riveting, or other known fixing method.

[0016] The intermediate regions 18 and 20 may have bores 28 and 30formed before, during or after the elongated blank 10 is cut from themetal sheet, to facilitate mounting of a universal joint cross-piece.The bores 28 and 30 are aligned on a diameter with respect to the axisof the shaft to ensure that the cross-piece pivots to provide propermounting of a coupling member also pivoted on the cross-piece, but at aright angle with respect to the diameter of the bores 28 and 30.Alternatively, bores 26 and 28 may be formed after the elongated blank10 is bent to form bent blank 22.

[0017] The central region 12 may have a bore 32 for facilitating themounting of a pivot member in alignment with the shaft. Typically, thepivot member is a spherical ball or a tubular socket. For example, acomplete double Cardan universal joint may comprise two yokes made fromtwo bent blanks 22, one bent blank 22 being equipped with a sphericalball and the other bent blank 22 being equipped with a tubular socket toreceive the spherical ball of the other bent blank 22. The pivoting ofthe spherical ball in the tubular socket controls the angle of thecoupling member that is mounted by means of a cross-piece in each bentblank 22.

[0018]FIG. 3 illustrates a variation of the bent shape of theintermediate regions 18 and 20 of the elongated blank 10. Specifically,arm portions 34 and 36 have concave surfaces 38 and 40 facing radiallyinwardly, such that the intermediate regions approximate longitudinalportions of a cylinder. This configuration is not required for thepractice of the invention; however, it may facilitate the insertion ofthe universal joint cross-pieces into the bores 28 and 30 and maystrengthen the intermediate regions by resisting flexing.

[0019] In the embodiment of FIGS. 1-3, the five regions have a width,defined crosswise with respect to the length of the elongated blank, andthe width of the central region 12 is less than the width of the two endregions 14 and 16. Also, the width of the intermediate regions 18 and 20is greater than the width of the central region 12 and greater than thewidth of the end regions 14 and 16. This configuration facilitates themounting of the cross-pieces and the insertion of the resulting yokesinto the coupling piece joining the two yokes. However, otherconfigurations may be employed with the present invention.

[0020] The overlapping end regions 14 and 16, with the shaft beingmounted on bores 24 and 26 that penetrate both layers of material, mayprovide a redundancy that improves the strength and reliability of theresulting yoke. Generally, no fixing together of the end regions 14 and16 is believed to be necessary. However, if desired, the end regions 14and 16 may be joined together, for example by welding, as illustrated byoptional weld 42, shown in FIG. 2.

[0021]FIG. 4 illustrates an elongated blank 44 according to anotherembodiment of the present invention. Elongated blank 44 comprises acentral region 46, two end regions 48 and 50, and two intermediateregions 52 and 54 between the central region 46 and the end regions 48and 50, respectively. Bores 56, 58 and 60 within the intermediate andcentral regions are similar to bores 28, 30 and 32, respectively, ofelongated blank 10. Relief areas 62 and 64, between the central region46 and the intermediate regions 52 and 54 facilitate bending ofelongated blank 44 at predetermined locations.

[0022] Note that end regions 48 and 50 of elongated blank 44 arerounded, in plan view, and have circular bores 66 and 68 to facilitatemounting of a shaft. This indicates the broad range of possible shapesof the resulting bent blank intermediate product and the range ofpossible finished yoke configurations. End regions 14 and 16 ofelongated blank 10 and end regions 48 and 50 of elongated blank 44 maybe modified somewhat, e.g., by trimmed end portions 70 and 72 of endregions 14 and 48, as shown, to facilitate overlapping of the endregions.

Having described the invention, what is claimed is:
 1. A method ofmaking a yoke for a double Cardan universal joint, the methodcomprising: cutting a metal sheet to provide an elongated blank havingfive regions defined along the length of the elongated blank, thedefined regions being a central region, two end regions, and anintermediate region between the central region and each of the two endregions; and bending the elongated blank such that the two end regionsof the elongated blank overlap and provide a mounting for a shaft suchthat a pivot member to be mounted on the central region of the elongatedblank will be in alignment, axially, with respect to the shaft.
 2. Themethod according to claim 1, further comprising the step of formingnoncircular bores in the end regions of the elongated blank such thatthe non-circular bores correspond with each other when the elongatedblank is bent, thereby providing a keyed mounting for the shaft.
 3. Themethod according to claim 2, wherein the non-circular bores arehexagonal apertures.
 4. The method according to claim 1, furthercomprising the step of forming a bore in the central region for mountingof the pivot member.
 5. The method according to claim 1, wherein thebending is, predominately, at predetermined locations of the elongatedblank such that the resulting yoke has a substantially rectangularlongitudinal section, with the central region of the elongated blankbeing parallel to and opposite the two overlapping end regions and withthe two intermediate regions being parallel and opposite each other. 6.The method according to claim 1, further comprising forming of boreswithin the two intermediate regions for mounting of a universal jointcross-piece within the bores, said step of forming the bores beingbefore the step of bending the elongated blank.
 7. The method accordingto claim 1, further comprising forming of bores within the twointermediate regions for mounting of a universal joint cross-piecewithin the bores, said step of forming the bores being after the step ofbending the elongated blank.
 8. The method according to claim 1, whereinthe five regions of the elongated blank have a width, measured crosswisewith respect to the elongated blank, and the width of the central regionis less than the width of the two end regions.
 9. The method accordingto claim 8, wherein the width of the intermediate regions is greaterthan the width of the central region and is less than the width of theend regions.
 10. The method according to claim 1, wherein the bending ofthe elongated blank results in the intermediate regions being curved, incross section, such that at least one concave surface of eachintermediate region projects radially inwardly, with respect to the axisof the shaft.
 11. The method according to claim 10, wherein theintermediate regions approximate longitudinal portions of a cylinder,with concave surfaces facing radially inwardly.
 12. A yoke for a doubleCardan universal joint, the yoke comprising: an elongated blank withfive regions defined along the length of the elongated blank, thedefined regions being a central region, two end regions, and anintermediate region located between the central region and each of thetwo end regions; and the elongated blank being bent such that the twoend regions of the elongated blank overlap and provide a mounting for ashaft such that a pivot member to be mounted on the central region ofthe elongated blank will be in alignment, axially, with respect to theshaft.
 13. A yoke for a double Cardan universal joint according to claim12, wherein the end regions of the elongated blank have non-circularbores that correspond with each other when the elongated blank is bent,thereby providing a keyed mounting for the shaft.
 14. A yoke for adouble Cardan universal joint according to claim 12, wherein thenon-circular bores are hexagonal apertures.
 15. A yoke for a doubleCardan universal joint according to claim 12, wherein the central regionof the elongated blank has a bore for mounting of the pivot member. 16.A yoke for a double Cardan universal joint according to claim 12,wherein the elongated blank is bent, predominately, at predeterminedlocations, such that the yoke has a substantially rectangularlongitudinal section, with the central region of the elongated blankbeing parallel to and opposite the two overlapping end regions and withthe two intermediate regions being parallel and opposite each other. 17.A yoke for a double Cardan universal joint according to claim 12,wherein the intermediate regions each have a bore for receiving auniversal joint cross-piece, the bores being aligned diametricallyopposite each other with respect to the axis of the shaft.
 18. A yokefor a double Cardan universal joint according to claim 12, wherein theintermediate regions are curved, in cross section, such that at leastone concave surface projects radially inwardly, with respect to the axisof the shaft.
 19. A yoke for a double Cardan universal joint accordingto claim 18, wherein the intermediate regions approximate longitudinalportions of a cylinder, with concave surfaces facing radially inwardly.20. A yoke for a double Cardan universal joint according to claim 12,wherein the five regions of the elongated blank have a width, measuredcrosswise with respect to the elongated blank, and the width of thecentral region is less than the width of the two end regions.
 21. A yokefor a double Cardan universal joint according to claim 20, wherein thewidth of the intermediate regions is greater than the width of thecentral region and less than the width of the end regions.
 22. A yokefor a double Cardan universal joint according to claim 12, wherein theoverlapping end regions are fixed together by welding.